A Review on Biological Control of Fungal Plant Pathogens Using Microbial Antagonists
ABSTRACT The objective of this study was to review the published research works on biological control of fungal plant diseases during past 50 years. Fungal plant pathogens are among the most important factors that cause serious losses to agricultural products every year. Biological control of plant diseases including fungal pathogens has been considered a viable alternative method to chemical control. In plant pathology, the term biocontrol applies to the use of microbial antagonists to suppress diseases. Throughout their lifecycle, plants and pathogens interact with a wide variety of organisms. These interactions can significantly affect plant health in various ways. Different mode of actions of biocontrol-active microorganisms in controlling fungal plant diseases include hyperparasitism, predation, antibiosis, cross protection, competition for site and nutrient and induced resistance. Successful application of biological control strategies requires more knowledge-intensive management. Various methods for application of biocontrol agents include: application directly to the infection court at a high population level to swamp the pathogen, application at one place in which biocontrol microorganisms are applied at one place (each crop year) but at lower populations which then multiply and spread to other plant parts and give protection against pathogens and one time or occasional application that maintain pathogen populations below threshold levels. Commercial use and application of biological disease control have been slow mainly due to their variable performances under different environmental conditions in the field. To overcome this problem and in order to take the biocontrol technology to the field and improve the commercialization of biocontrol, it is important to develop new formulations of biocontrol microorganisms with higher degree of stability and survival. Majority of biocontrol products are applied against seed borne and soil borne fungal pathogens, including the causal agents of seed rot, damping-off and root rot diseases. These products are mostly used as seed treatment and have been effective in protecting several major crops such as wheat, rice, corn, sugar beet and cotton against fungal pathogens. However, in some cases, biocontrol microorganisms have also been tested as spray application on foliar diseases, including powdery mildew, downy mildew, blights and leaf spots. A few post harvest fungal diseases have also been controlled by the use of antagonistic fungi and bacteria. Biocontrol microorganisms are also being used as the form of composts in some plants. Research data and observations in nurseries have shown that addition of composted organic matter to potting mixes results in suppression of soil borne diseases. A significant improvement have been made in different aspects of biological control of fungal plant diseases, but this area still need much more development and investigations to solve the existing problems. In order to have more effective biological control strategies in the future, it is critical to carry out more research studies on some less developed aspects of biocontrol, including development of novel formulations, understanding the impact of environmental factors on biocontrol agents, mass production of biocontrol microorganisms and the use of biotechnology and nano-technology in improvement of biocontrol mechanisms and strategies. Future outlooks of biocontrol of plant diseases is bright and promising and with the growing demand for biocontrol products among the growers, it is possible to use the biological control as an effective strategy to manage plant diseases, increase yield, protect the environment and biological resources and approach a sustainable agricultural system.
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ABSTRACT: Abstract: Rhizomania is one of the most important diseases of sugar beet around the world – including in Iran. The disease causes a severe decrease in sugar yield and is a limiting factor in sugar beet cultivation. Control of the disease is very difficult due to the longterm survival of its fungal vector (Polymyxa betae) in the soil. In this study, we investigated the effects of antagonistic fungal isolates on the population of the resting structure (cystosorus) of P. betae, under greenhouse conditions. Antagonistic fungi, including Trichoderma harzianum and Talaromyces flavus, were isolated from soil samples collected from sugar beet infested fields in the Semnan Province of Iran. In the next step, their inocula were prepared through reproduction on rice bran. For evaluation of the efficacy of antagonists in greenhouse conditions, a split plot trial was conducted and performed. The main factor was three different methods of application of T. flavus as the soil treatment, seed treatment, and a combination of both methods. The sub-factor was the use of different fungal isolates. To determine the cystosorus population of the fungal vector, seedling roots in all treatments were stained with lactic acid and fuchsine (lactofushine), 60 days after sowing. The number of cystosorus in one gram of root was counted using a light microscope and hemocytometer. At the end of the study, average root weight in different treatments was also measured to select and introduce the best treatments in regard to their effects on root weight. According to the results, the number of cystosorus in 1 g of root was different in various treatments and those treatments containing TF-Su-M-1, TF-Su-M-2, TH-Su-M-1, and TH-Su-M-2 used as a soil application method were more effective in the reduction of the cystosorus population and root weight increase. Among the above-mentioned treatments, maximum reduction of cystosori population and the increase in root weight were observed in TH-Su-M-1 and TF-Su-M-2 through the soil application method.Journal of Plant Protection Research 04/2014; 54.
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ABSTRACT: Biological control potential of fungi isolated from roots of diseased tomato plants against fungi associated with foliar diseases of tomato was investigated in this study. Fungi associated with the diseased tomato leaves included Alternaria alternata, Fusarium solani, Phialophora melinii, Paecilomyces variotii, and Verticillium albo-atrium. Each fungus was paired against Trichoderma harzianum and Trichoderma koningii which were isolated from the rhizophere of the diseased plants. The antagonists (Trichoderma species) were paired simultaneously against the pathogen, the pathogen before the antagonist and the antagonist before the pathogen. For the timing of inoculation, pairing of the antagonist before the pathogen was the most effective, followed by simultaneous pairing, while pathogen before antagonist gave the least antagonism after nine days of inoculation. The mode of antagonism was found to be by competition for space, antibiosis and mycoparasitism.Nature and Science of Sleep 07/2013; 11(7):124-128.
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ABSTRACT: Many studies have shown that several Greek ecosystems inhabit very interesting bacteria with biotechnological properties. Therefore Streptomyces isolates from diverse Greek habitats were selected for their antifungal activity against the common phytopathogenic fungus Fusarium oxysporum. The isolate encoded ACTA1551, member of Streptomyces genus, could strongly suppress the fungal growth when examined in antagonistic bioassays in vitro. The isolate was found phylogenetically relative to Streptomyces rochei after analyzing its 16S rDNA sequence. The influence of different environmental conditions, such as medium composition, temperature, and pH on the expression of the antifungal activity was thoroughly examined. Streptomyces rochei ACTA1551 was able to protect tomato seeds from F. oxysporum infection in vivo while it was shown to promote the growth of tomato plants when the pathogen was absent. In an initial effort towards the elucidation of the biochemical and physiological nature of ACTA1551 antifungal activity, extracts from solid streptomycete cultures under antagonistic or/and not antagonistic conditions were concentrated and fractionated. The metabolites involved in the antagonistic action of the isolate showed to be more than one and produced independently of the presence of the pathogen. The above observations could support the application of Streptomyces rochei ACTA1551 as biocontrol agent against F. oxysporum.BioMed research international. 01/2013; 2013:387230.